Barack Obama's long-awaited decision on how many troops to bring home from Afghanistan is overshadowing the defence merry-go-round taking place this summer.

Robert Gates, the defence secretary, who has presided over the Afghanistan and Iraq wars for 4 1/2 years, is retiring next week. The top two American generals in Kabul – David Petraeus and David Rodriguez – are due to leave for new assignments as early as July. Also departing in July is retired Army Lt. Gen. Karl Eikenberry, the US ambassador in Kabul who in 2006-07 served as the top commander of US forces in Afghanistan.

They will be replaced by men with military and national security resumes but less direct experience in Afghanistan.

This changing of the guard is not intended to steer the administration's Afghan war policy in a new direction. Yet a fresh set of eyes and ears could lead to new advice to the White House on how to wind down 10 years of conflict in the country that provided haven to al-Qaida prior to the Sept. 11 terrorist attacks.

It coincides with Mr Obama's decision, to be announced Wednesday, on how to fulfil his promise to begin a withdrawal of US forces in July. He made that pledge in December 2009 when he announced he was ordering an extra 30,000 US troops to Afghanistan in an effort to reverse the momentum of the Taliban insurgency.

The goal remains to turn over Afghan security responsibility to the Afghans by the end of 2014. Between now and that target date, all U.S. and other foreign troops are to be out of the country.

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Mr Gates said during a visit to Afghanistan earlier this month that it is too soon to adjust strategy, even taking into account the impact of the May 2 killing of al-Qaida leader Osama bin Laden in Pakistan.

Mr Gates also has cautioned against a rapid drawdown of US forces. He has argued that more time is needed to pound the Taliban to the point where its leaders will feel compelled to engage in serious peace talks. On the other hand, the administration knows the US public is weary of war – its human and financial costs.

Leon Panetta, the CIA director who is expected to win Senate confirmation Tuesday to succeed Mr Gates as Pentagon chief on July 1, has not been expansive in public about his views on Afghanistan. Mr Panetta is to be replaced as head of the spy agency by Gen Petraeus, who will retire from the Army to take that job if confirmed by the Senate.

Mr Gates, Gen Petraeus and Navy Adm. Mike Mullen, the Joint Chiefs chairman who will retire Oct. 1, have been among the administration's strongest advocates of a troop-intensive approach to the war. Their departure could create a shift in the balance of war advice within the administration, says Stephen Biddle, a defence analyst at the Council on Foreign Relations who has periodically advised US commanders in Kabul and Baghdad.

"You're replacing people that had a very distinct perspective and were very effective proponents of that view," Mr Biddle said. It is unlikely, he said, that the incoming team – headed by Mr Panetta – will be as unified in its views or as effective in promoting them.

Taking Gen Petraeus' place as commander of all US and Nato forces will be Marine Lt. Gen. John R. Allen, assuming he is confirmed by the Senate. He has not served in Afghanistan but has extensive knowledge of the conflict from his nearly three years as deputy commander of US Central Command, which oversees the war.

Mr Eikenberry in particular has had rocky relations with the Afghan president. On Sunday he publicly reproached Karzai for painting American forces as occupiers and enemies. His successor, Ryan Crocker, knows Mr Karzai; he reopened the U.S. Embassy in Kabul after the 2001 toppling of the Taliban regime.